LED heat lamp arrays for CVD heating

ABSTRACT

A reactor chamber is positioned between a top array of LED heat lamps and a bottom array of LED heat lamps. The LED heat lamps forming the top and bottom arrays are individually or controllable in groups such that power output along each array of LED heat lamps can dynamically differ. The LED lamps can be controlled in response to, for example, feedback from chamber sensors, a desired temperature profile, and a failed LED lamp. In this way, the methods and systems described herein can dynamically compensate for operational characteristics of the reactor chamber. In one configuration, the LED heat lamps are arranged in a rectangular pattern. In some configurations, the LED heat lamps are arranged in a circular or a concentric pattern.

RELATED CASES

This application is a continuation of application Ser. No. 10/217,230,filed Aug. 9, 2002, now U.S. Pat. No. 6,818,864 and titled LED HEAT LAMPARRAYS FOR CVD HEATING, which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to heat lamps. Morespecifically, the present invention relates to heat lamps for improvingthe temperature uniformity in a field heated by one or more LED heatlamps.

2. Related Art

Chemical vapor deposition (CVD) is a very well known process in thesemiconductor industry for forming thin films of materials onsubstrates, such as silicon wafers. In a CVD process, gaseous moleculesof the material to be deposited are supplied to wafers to form a thinfilm of that material on the wafers by chemical reaction. Such formedthin films may be polycrystalline, amorphous or epitaxial. Typically,CVD processes are conducted at the elevated temperatures to acceleratethe chemical reaction and to produce high quality films. Some processes,such as epitaxial silicon deposition, are conducted at extremely hightemperatures (>900° C.).

To achieve the desired high temperatures, substrates can be heated usingresistance heating, induction heating or radiant heating. Among theseheating techniques, radiant heating is the most efficient technique and,hence, is the currently favored method for certain types of CVD. Radiantheating involves positioning infrared lamps around a reaction chamberpositioned within high-temperature ovens, called reactors.Unfortunately, radiant energy has a tendency to create nonuniformtemperature distributions, including “hot spots,” due to the use oflocalized radiant energy sources and consequent focusing andinterference effects.

During a CVD process, one or more substrates are placed on a wafersupport (i.e., susceptor) inside a chamber defined within the reactor(i.e., the reaction chamber). Both the wafer and the support are heatedto a desired temperature. In a typical wafer treatment step, reactantgases are passed over the heated wafer, causing chemical vapordeposition (CVD) of a thin layer of the desired material on the wafer.If the deposited layer has the same crystallographic structure as theunderlying silicon wafer, it is called an epitaxial layer. This is alsosometimes called a monocrystalline layer because it has only one crystalstructure. Through subsequent processes, these layers are made intointegrated circuits, producing from tens to thousands or even millionsof integrated devices, depending on the size of the wafer and thecomplexity of the circuits.

Various process parameters must be carefully controlled to ensure a highquality of layers resulting from CVD. One such critical parameter is thetemperature of the wafer during each treatment step of wafer processing.During CVD, for example, the wafer temperature dictates the rate ofmaterial deposition on the wafer because the deposition gases react atparticular temperatures and deposit on the wafer. If the temperaturevaries across the surface of the wafer, uneven deposition of the filmoccurs and the physical properties will not be uniform over the wafer.Furthermore, in epitaxial deposition, even slight temperaturenon-uniformity can result in crystallographic slip.

In the semiconductor industry, it is important that the material bedeposited uniformly thick with uniform properties over the wafer. Forinstance, in Very Large and Ultra Large Scale Integrated Circuit (VLSIand ULSI) technologies, the wafer is divided into individual chipshaving integrated circuits thereon. If a CVD process step producesdeposited layers with nonuniformities, devices at different areas on thechips may have inconsistent operation characteristics or may failaltogether.

SUMMARY OF THE INVENTION

The systems and methods of the present invention have several features,no single one of which are solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, its more prominent features will now bediscussed briefly. After considering this discussion, and particularlyafter reading the section entitled “Detailed Description of thePreferred Embodiments,” one will understand how the features of thisinvention provide several advantages over traditional CVD heatingmethods and systems.

One aspect is a chemical vapor deposition apparatus that comprises ahigh temperature processing chamber and a susceptor disposed within thechamber for supporting a wafer to be processed, the susceptor comprisinga top surface, a bottom surface, and a perimeter. The apparatus furthercomprises a plurality of light emitting diodes (LEDs) located on asurface of the chamber, each configured to emit radiant energy towardsthe top surface, and a controller configured to adjust the radiantenergy emitted by at least one of the plurality of LEDs relative toanother one of the plurality of LEDs.

Another aspect is a method of processing a semiconductor in a chamber byapplying heat from an array of LED lamps disposed adjacent to thechamber, each LED lamp being configured to emit directional radiantenergy towards a substrate in the chamber. The method comprisesinserting a wafer in a chamber, sensing an operational status of aplurality of LED lamps, if an LED from the plurality of LED lamps isnon-operational, then adjusting a planned temperature profile for theplurality of LED lamps to compensate for the non-operational LED lamp.The method further includes applying heat from the plurality of LEDlamps to the wafer, identifying nonuniformities in the temperature ofthe wafer, and adjusting an energy level output of at least one of theplurality of LED lamps with respect to another one of the plurality ofLED lamps to compensate for the nonuniformity.

Still another aspect is a semiconductor processing apparatus thatcomprises a chamber defined by at least one wall, a structure forsupporting a substrate within the chamber, and at least one LED heatlamp array disposed proximate to the chamber.

Yet another aspect is an apparatus for processing semiconductor wafersat elevated temperatures that comprises a high temperature processingchamber defined by at least one wall, a susceptor disposed within thechamber for supporting a wafer to be processed, the susceptor comprisinga top surface, a bottom surface, a perimeter, a first array of LED heatlamps being disposed proximate to the susceptor, and at least one LEDlamp of the first array of LED heat lamps configured to emit directionalradiant energy in a first direction towards the top surface. Theapparatus further comprises a first perforated reflector located betweenthe first array of LED heat lamps and the susceptor, the perforationsbeing aligned with the at least one LED lamp of the first array and asecond array of LED heat lamps being disposed proximate to the susceptorand parallel to the first array of LED heat lamps, the susceptor beingdisposed between at least a portion of the first array of LED heat lampsand said second array of LED heat lamps. The apparatus still furthercomprises at least one LED lamp of the second array of LED heat lampsconfigured to emit directional radiant energy in a second directiontowards the bottom surface, both of the directions being at leastpartially disposed within a volume defined by the susceptor perimeter ina direction normal to the susceptor, and a second perforated reflectorlocated between the second array of LED heat lamps and the susceptor,the perforations being aligned with the at least one LED lamp of thesecond array.

Another aspect is a chemical vapor deposition apparatus that comprises aprocess chamber having an area for horizontal positioning of a substratewithin a substrate treatment zone and having chamber walls forconducting a flow of gas across a surface of the substrate, a firsttwo-dimensional array of heat lamps being disposed generally above thesubstrate treatment zone, each LED of the first two-dimensional array ofheat lamps having a length and a width so that the first two-dimensionalarray of heat lamps spans the substrate treatment zone in a first rowand spans the substrate treatment zone in a first column generallyperpendicular to the first row. The apparatus further comprises a firstperforated reflector located between the first two-dimensional array ofheat lamps and the substrate, the perforations being substantiallyaligned with the first two-dimensional array of heat lamps, a secondtwo-dimensional array of heat lamps being disposed generally below saidsubstrate treatment zone, each LED of the second two-dimensional arrayof heat lamps having a length and a width so that the secondtwo-dimensional array of heat lamps spans the substrate treatment zonein a second row and spans the substrate treatment zone in a secondcolumn, at least one LED from the second row or second column havingmeans for adjusting energy lamp output relative to another of the LEDsfrom the same second row or column, and a second perforated reflectorlocated between the second two-dimensional array of heat lamps and thesubstrate, the perforations being substantially aligned with the secondtwo-dimensional array of heat lamps.

Still another aspect is a method of processing a substrate in a chamberby applying heat from an LED lamp disposed adjacent to the chamber, theLED lamp being configured to emit directional radiant energy towards thesubstrate. The method comprises inserting a wafer in a chamber, applyingheat from the LED lamp to the wafer, identifying nonuniformities in thetemperature of the wafer, and adjusting an energy level output of theLED lamp to compensate for the nonuniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will now be described with reference to the drawings ofseveral preferred embodiments, which embodiments are intended toillustrate and not to limit the invention.

FIG. 1 is a perspective view of one embodiment of a process chamber thatcan implement light emitting diode lamps having certain features,aspects and advantages of the invention.

FIG. 2 is a cross-sectional view of the chamber of FIG. 1 taken alongthe line 2—2.

FIG. 3 is a perspective cross-sectional view of one-half of the processchamber of FIG. 1 taken along the line 3—3.

FIG. 4 is a top plan view of the chamber of FIG. 1 with certain internalcomponents being shown with dashed lines.

FIG. 5 is a view of the inlet end of the chamber of FIG. 1 with certaininternal components being shown with dashed lines.

FIG. 6 is a view of the outlet end of the chamber of FIG. 1 with certaininternal components being shown with dashed lines.

FIG. 7 is a side elevational view of the chamber of FIG. 1 with certaininternal components being shown with dashed lines.

FIG. 8 is a cross-sectional view illustrating the chamber connected to aportion of a wafer processing system.

FIG. 9 is a cross-sectional view illustrating a processing systemenvironment that includes an arrangement of radiant LED heat lampsdisposed above and below another chamber configuration.

FIG. 10 is a top cross-sectional view of a portion of the chamber ofFIG. 9 taken along the line 10—10, illustrating an array of radiant LEDheat lamps disposed below an exemplary susceptor.

FIG. 11 is the same view as FIG. 10 except that the susceptor is shownin ghost.

FIG. 12 is a detailed cross-section view of a portion of one row of LEDheat lamps from FIG. 11 taken along the line 12—12.

FIG. 13 is a schematic view of the heating system of the presentinvention and also shows electrical connections to a suitable heatercontrol module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

U.S. Pat. No. 4,836,138, which issued on Jun. 6, 1989 to Robinson etal., and U.S. Pat. No. 4,828,224, which issued on May 9, 1989 to Crabbet al., both of which are hereby expressly incorporated by reference,described exemplary cold-wall single wafer reaction chambers. Thesereaction chambers are exemplary environments that can be modifiedaccording to the teachings of this patent. For example, LED heat lampsand arrays of LED heat lamps can be used in accordance with certainfeatures, aspects and advantages of the present invention. In onepreferred arrangement, the LED heat lamps and arrays are used in CVDchambers. In a more preferred arrangement, the LED heat lamps are usedin CVD chambers that have been optimized for epitaxial deposition.

U.S. Pat. No. 6,093,252, which issued on Jul. 25, 2000 to Wengert etal., also disclosed a reaction chamber configuration that can bemodified to use LED heat lamps and arrays of LED heat lamps havingcertain features, aspects and advantages in accordance with the presentinvention. The disclosure of that patent is hereby expresslyincorporated by reference.

With reference now to FIGS. 1–8, an exemplary reactor chamber 10 forchemical vapor processing and the like is illustrated. As can be seen,the chamber 10 has an elongated, generally flattened configuration,which in cross section has a generally lenticular shape. A lenticularshape has opposed biconvex surfaces which may have circular curvatures.In some configurations, the chamber can have other outer shapes, such assquare, rectangular and the like. For instance, a square chamber isdisclosed in U.S. Pat. No. 6,143,079, which issued on Nov. 7, 2000, andwhich is hereby incorporated by reference in its entirety. Theillustrated chamber of FIGS. 1–8 has an upper wall 12 with an outerconvex surface and an inner concave surface, and a lower wall 14 with anouter convex surface and an inner concave surface. The walls 12 and 14are connected by vertically short side rails 16 and 18. These walls andside rails are further joined by an upstream inlet end flange 20 and adownstream outlet end flange 22. Upstream and downstream relate to thedirection of process gas flow, as will be described, and are synonymousin the present description with front and rear.

With reference now to FIG. 2, both the upper wall 12 and the lower wall14 are thin, curved plate-like elements having a rectangular flatvertical projection. The walls 12 and 14 desirably have a circularradius of curvature and may be formed by segments cut from a cylindricaltube made of quartz or similar material. In larger chambers, the walls12 and 14 may be constructed by heating and forming flat quartz plates.Although quartz is preferred, other materials having similar desirablecharacteristics may be substituted. Some of these desirablecharacteristics include a high melting point, the ability to withstandlarge and rapid temperature changes, chemical inertness, and a hightransparency to light.

The thick side rails 16, 18 may be machined from a quartz rod ofrectangular cross section or otherwise formed into the cross sectionalshape illustrated in FIG. 2. More specifically, each side rail 16, 18includes a reinforced main body having an upper surface 24 that forms acontinuation of the curved exterior surface of the upper wall 12, and alower surface 26 which is curved to form a continuation of the exteriorsurface of the lower wall 14. The laterally exterior surface 28 of eachside rail 16, 18 is flat and extends vertically. The interior surface ofeach side rail 16, 18 is formed with longitudinally extending upper andlower recesses 30 a, 30 b that create upper, middle and lower stub wallsegments 32 a, 32 b, 32 c, respectively. The upper and lower stub wallsegments 32 a, 32 c mate with the side edges of the upper and lowerwalls 12 and 14 at longitudinal weld joints 39. In one embodiment, themain body of the side rails 16, 18 has a thickness or width dimension ofabout 20 mm and a height of about 21 mm.

In the illustrated arrangement, a support or stringer preferably isprovided in the form of a flat, rectangular plate 40 that extendsbetween the side rails 16 and 18. As seen in FIG. 4, the support plate40 includes an aperture 42 defining a void or opening 44 extendingacross the width of the chamber 10 and dividing the support plate 40into an inlet section 46 a and an outlet section 46 b. The inlet section46 a extends from the inlet flange 20 to an upstream edge of the opening44, and the outlet section 46 b extends from a downstream edge of theopening 44 to the outlet flange 22. As may be seen from FIG. 4, theinlet section 46 a of the support plate is shorter in the longitudinaldirection than is the outlet section 46 b. More specifically, in apreferred arrangement, the inlet section is about 70% of the length ofthe outlet section. That proportional arrangement generally relates tothe process gas flow through the chamber.

As best seen in FIG. 2, each of the side rails 16 and 18 includes theinwardly extending central stub wall 32 b that in effect forms anextension of the support plate 40. In this respect, the support plate 40in practice terminates at the main body of the side rails 16, 18, or, inother words, at the laterally outer extent of the recesses 30 a, 30 b.Longitudinal joints 48 indicate the welded connection between thelateral edges of the support plate 40 and the central stub walls 32 b ofeach of the side rails 16 and 18. The central stub walls 32 b preciselybisect the upper and lower walls 12 and 14, and the support plate 40thus lies on the exact centerline or center plane therebetween.

With reference to FIGS. 1 and 3, each of the end flanges 20, 22 compriseouter, generally rectangular slabs 50, 51, respectively, havingchamfered corners 52 and inner lenticular shaped extensions 54. Withreference now to FIGS. 1 and 3, the inner extensions 54 conform to theshapes of the upper and lower walls 12, 14 and the central support plate40. More particularly, short longitudinal portions extend from the slabs50, 51 to join with each of these plate-like members 12, 14, 40. At eachend of the chamber 10, curvilinear weld joints 56 are formed between thecurved upper and lower walls 12, 14 and the upper and lower portions ofthe extensions 54, while linear joint lines 58 are defined betweencentral portions of the extensions 54 and the longitudinal ends of thesupport plate 40.

The slab 50 of the inlet flange 20 includes a laterally extendingaperture 60 (see FIG. 3) in an upper portion which leads into an upperregion 66 (see FIG. 2) within the chamber 10 above the support plate 40and below the upper wall 12. The slab 51 of the outlet flange 22, incontrast, includes a pair of laterally extending apertures 62, 64 (seeFIG. 3); the upper aperture 62 communicates with the upper region 66(see FIG. 2) of the chamber 10 previously described, while the loweraperture 64 communicates with a lower region 68 (see FIG. 2) of thechamber 10 defined below the support plate 40 and above the lower wall14. The rounded recesses 30 a, 30 b in the side rails 16, 18 definelateral boundaries of the upper and lower regions 66, 68. As will bedescribed below, the wafer processing is done in the upper region 66only, with the support plate 40 defining the lower boundary of theprocess zone.

The opening 44 in the support plate 40 is dimensioned to receive asusceptor 70, as illustrated in FIGS. 3 and 8, and a temperaturecompensation ring 72 (see FIGS. 4 and 8), which surrounds the susceptor70. The temperature compensation ring 72 has a thermal mass configuredto help increase temperature uniformity in the chamber. In oneconfiguration, the ring itself is asymmetric relative to a wafer beingprocessed, such that the ring has a different center of thermal massthan the wafer or an uneven distribution of thermal mass about thewafer. For instance, in one arrangement, the ring can have asubstantially rectangular outer perimeter that results in high thermalmass concentrations at the corners but a similar center of thermal massrelative to the wafer. In other arrangements, the ring can have anoff-center configuration (e.g., the illustrated elongated rectangle) inwhich the distribution of thermal mass about the wafer is uneven. Forinstance, the ring can receive the wafer in a location other than itscenter. Of course, the ring can be triangular, circular, elliptical, orany other suitable shape, depending in part upon the geometry of otherfeatures in the chamber and the gas flow path.

The susceptor 70 is adapted to rotate within the stationary ring 72 andis preferably spaced therefrom across a small annular gap G of about 0.5to 1.0 mm. The centerline of a generally circular temperaturecompensation ring 72 is schematically illustrated in FIG. 4 by thebroken line circle 74 shown therein. The shape of the aperture 42 in thesupport plate 40 surrounding the ring 72 can also be made circular sothat the edges of the opening 44 would be in close proximity to thering. However, it has been found that somewhat of a rectangular aperture42 having rounded corners, as shown in FIG. 4, is preferred. The supportplate sections 46 a, 46 b may be cut to provide those exact shapes; orfor manufacturing convenience, short, somewhat triangular sections 76 offill, shown in FIG. 4, may be welded to the plate sections and thechamber side rails 16, 18 to provide the desired configuration.

It will be noted that the circle 74 shown in FIG. 4, which representsthe centerline of the temperature compensation ring 72 (see FIG. 8), isneither centrally positioned with respect to the upstream and downstreamends of the chamber, nor with respect to opening 44. Instead, theupstream or leading edge of the circle 74 is closer to the downstreamedge of the inlet plate section 46 a than is the downstream or trailingedge of the circle to the upstream edge of the outlet plate section 46b. This arrangement helps maintain the strength of the chamber byreducing the rate of devitrification of the upstream edge of the outletplate section 46 b. That is, the gas flow heats up as it passes over thesusceptor so that the temperature in the chamber walls tends to be thegreatest just downstream from the susceptor. The upstream edge cantherefore be exposed to significant thermal cycling and devitrificationif too close to the susceptor, and thus the susceptor is offsetforwardly within the opening 44 to increase the spacing therebetween.

In some configurations, the offset arrangement discussed directly abovealso affects the flow of the process gases through the chamber. Moreparticularly, the wafer placed upon the susceptor which is surrounded bythe ring is positioned close to the downstream edge of the inlet platesection 46 a to minimize the amount of reaction gases which pass throughthe opening 44 upstream of the wafer. This minimizes the amount ofreaction gas which can deposit underneath the susceptor in the lowerportion 68 of the chamber 10. It also should be noted that thisconfiguration increases the difficulty in obtaining a uniformtemperature region proximate the wafer.

With continued reference to FIGS. 4 and 8, the temperature compensationring 72 is supported by three elbow-shaped support elements havingvertically extending portions being welded to the support platesections. More specifically, a front support element or finger 80 iswelded to the rear of the front plate section 46 a midway between therails 16, 18 of the chamber, and the horizontal portion of the finger orelement 80 extends rearwardly into the opening 44 so as to be positionedunder the leading edge of the temperature compensation ring 72. A pairof spaced elements or fingers 82 have elongated horizontal portions thatextend forwardly beneath the trailing edge of the compensation ring 72as seen in FIG. 8, as well as FIGS. 2–7. Preferably, each of the fingersor elements 80, 82 includes a pin (not shown) that underlies thecompensation ring 72. The compensation ring 72 is thus supported in ahorizontal plane at three points by upstanding pins (not shown) in thefingers or elements 80, 82. The pins may eventually deteriorate fromrepeated thermal cycling and exposure to process etch gases, but theycan be replaced fairly readily.

In FIG. 8, a susceptor 70 is shown supported on arms 86 of a suitablesupport 88 connected to the upper end of a rotatable shaft 90 thatextends through a tube 92 depending from the bottom wall of the chamber.The susceptor 70 is shown approximately level with the upper edge of thering 72 and with the upper surface of the support plate 40. This enablesa wafer to be positioned above the susceptor 70 and in the upper portion66 of the process chamber 10.

Still referring to FIG. 8, the inlet flange 20 is adapted to beconnected to an inlet component 94 having a horizontally elongated slot96 through which a wafer may be inserted, and having an elongated inlet98 for introducing process gas into the upper portion 66 of the chamberafter an isolation valve leading from the slot 96 to a wafer handlingchamber (not shown) has been closed. Correspondingly, the outlet flange22 is adapted to mate with an outlet component 100 for exhaustingprocess gas 112 from the chamber 10, as well as applying a vacuum to thechamber. As can be seen from FIG. 8, the outlet flange 22 is open to thelower portion 68 of the chamber beneath the support plate as well as theportion 66 above the support plate.

A plurality of temperature sensing devices, for example, thermocouples102, extends through the outlet component 100 and into the lower portion68 of the process chamber. The thermocouples 102 extend into proximityof the susceptor 70 to sense the local temperature surrounding thesusceptor 70 and wafer positioned there above. As has been describedpreviously in U.S. Pat. No. 6,093,252, the advantageous positioning ofthe sensing ends of the thermocouples 102 surrounding the susceptor 70allows comprehensive feedback regarding the temperature of the wafer andenables adjustment of radiant light emitting diode (LED) heat lamparrays 108, which will be described later, to compensate for temperatureirregularities. More particularly, a leading edge thermocouple 104terminates proximate the front end of the susceptor 70, a trailing edgethermocouple 106 terminates proximate a rear edge of the susceptor and alateral thermocouple (not shown) terminates proximate a lateral edge ofthe susceptor. Each of the thermocouples 102 enters the temperaturecompensation ring 72 which is formed of two parts to provide a hollowinterior therein. Again, this ring has been described previously in U.S.Pat. No. 6,093,252, which is hereby expressly incorporated by reference.

Preferably, the temperature compensation ring 72 is constructed ofgraphite or other such high heat absorbency material. The ring 72provides several advantages in the processing environment, primarilyreducing edge heat losses from the susceptor 70. More specifically, thering 72 closely surrounds the edge of the susceptor 70 and is maintainedat a similar temperature during processing, as the materials aresimilar. The susceptor and ring thus radiate heat toward one another togreatly reduce any radiant losses therebetween. Another advantage of thetemperature compensation ring 72 is preheating and postheating of thereactant gas in the region of the wafer. Specifically, the reactant gasenters the chamber at an ambient, non-reacting temperature and is heatedto a temperature suitable for deposition as it passes over the susceptorand wafer. The surrounding temperature compensation ring 72 thuspreheats the reactant gas stream before it reaches the leading edge ofthe susceptor, and, subsequently, the leading edge of the wafer. Theprocess gas thus reaches an approximately steady state temperaturebefore traveling over the edge of the wafer. Additionally, thetemperature of the gas does not significantly drop off after passing thedownstream edge of the wafer as the temperature compensation ring 72extends the downstream heating region. In some arrangements, the ringmay be elongated in a downstream direction such that the temperaturedrop occurs further downstream from the wafer.

The gas flow through the chamber is shown in FIG. 8. Reactant gas entersthrough the inlet component 94 with a predetermined lateral velocityprofile, such as the profile described in U.S. Pat. No. 5,221,556, theentirety of which is hereby expressly incorporated by reference. Thepredetermined velocity profile provides a larger gas flow towards thecentral portion of the reaction chamber 10 than the laterally outeredges to compensate for the longer deposition travel path over thecenter of the circular wafer supported on the susceptor 70. In otherwords, a greater amount of reactant gas is provided over the centralportion of the wafer due to reactant depletion along that flow path overthe wafer.

The reactant gas continues longitudinally rearward as indicated by arrow112 and exits through the outlet component 100 and downward throughexhaust conduits 114, as indicated with arrow 116. Typically, purge gasis supplied upward through the hollow tube 92 surrounding the shaft 90,the tube being sized to provide a gas passage surrounding the shaft. Thepurge gas enters the lower portion 68 of the chamber 10 as indicated byarrows 118. The purge gas prevents unwanted deposition of particulatesunderneath the susceptor 70 and exits through the lower longitudinalaperture 64 in the outlet flange 22, as indicated by arrow 120. Thepurge gas then mixes with the spent reaction gas and continues downalong the path of arrow 116 through the exhaust conduits 114.

With reference again to FIGS. 1–7, the end flanges 20, 22 are preferablytranslucent and fabricated from quartz having nitrogen bubbles dispersedtherein. The central thin walls 12, 14 and support plate 40, on theother hand, are transparent to radiant energy, allowing radiant heatingof the susceptor and wafer in the chamber 10, without creating hightemperatures in these structures. The translucent flanges 20, 22 scatterradiant energy to reduce “light-piping” therethrough. This protects0-rings 122 outside of the flanges 20, 22 from exposure to extremetemperatures generated within the chamber 10. Preferably, a section ofthe tube 92 below the lower wall 14 is similarly translucent fromnitrogen bubbles dispersed therein.

FIG. 9 illustrates a particular arrangement of components surrounding areaction chamber 130 that can be used for CVD processing. Reactionchamber 130 is similar to the chamber 10 described with reference toFIGS. 1–8. The chamber 130 includes an inner support plate 132 which issimilar to the inner support plate 40 as previously described, and thusincludes an aperture 133 formed therein. The aperture 133 is sized toreceive a temperature compensation ring 155 and a susceptor 134 forsupporting a semiconductor wafer. The support plate 132 is divided intoa front section 135 a upstream of the aperture 133 and a rear section135 b downstream of the aperture 133. The susceptor 134 is positioned ona plurality of radially extending arms 136 of a central hub 138 mountedon a hollow shaft 140. The shaft 140, in turn, is rotated by a motor 142disposed below the chamber 130. The rotational coupling between themotor 142 and the shaft 140 is explicitly described in U.S. Pat. No.6,093,252, previously incorporated by reference. The motor 142preferably is mounted on a fixed frame and includes adjustmentmechanisms for properly positioning the susceptor 134 within the chamber130.

At least one LED heat lamp array is arranged around the reaction chamber130 to heat the susceptor 134 and any wafer thereon. A first array ofupper LED lamps 146 is arranged above the chamber 130. A second lowerarray of LED lamps 148 is arranged below the chamber 130. In anotherembodiment, the at least one LED heat lamp array comprises a single LEDlamp configured to heat the susceptor 134 and the wafer.

The second lower array of LED lamps 148 may or may not be aligned withthe first array of upper LED lamps 146. The distribution of the upperarray of LED lamps 146 is unimpeded so that a regular sequence of LEDlamps is provided across the surface of the chamber 130. The lower arrayof LED lamps 140, on the other hand, is provided across the surface ofthe chamber 130 except in the region of the shaft 140. Thus, one or morespot lights or directed lamps 150 are positioned under the chamber 130and surround a downwardly extending quartz tube 152 formed integrallywith the chamber 130. The tube 152 concentrically receives the shaft140. The tube 152 and shaft 140 create an annular space therebetweenwhich is used to inject a purge gas into a region underneath thesusceptor 134. The directed lamps 150 radiate energy to the underside ofthe susceptor 134, which may be shadowed by the shaft 152 and supportingstructure. The specific heating arrangement for the directed lamps 150is similar to that described and illustrated in U.S. Pat. No. 4,836,138,which is hereby expressly incorporated by reference.

The upper and lower arrays of LED lamps 146, 148 are distributed in agenerally rectangular configuration above and below, respectively, thesusceptor region 134. This arrangement, in combination with the directedlamps 150, focuses the radiant energy on the susceptor 134 and theassociated wafer. Different arrangements and locations of the upper andlower arrays of LED lamps can be used. For example, the upper and/orlower arrays of LED lamps could be arranged in a concave fashion.

The orientation of the upper and lower arrays of LED lamps 146, 148 withrespect to one another further enhances uniformity of heating of thesusceptor 134. Generally, the LED lamps 146, 148 can receive the samepower levels or receive differing power levels to account for endeffects and other phenomena that can vary the temperature gradientacross the wafer. A configuration for supplying the differing powerlevels to the LED lamps 146, 148 is described with reference to FIG. 13.

An enlarged temperature compensation ring 155 is shown in FIG. 9. Itshould be noted, however, that the peripheral shape of the modifiedtemperature compensation ring 155 is generally rectangular and the shapegenerally conforms to the radiant heat from the upper and lower arraysof LED lamps 146, 148. This arrangement is highly efficient and resultsin more uniform temperatures across the susceptor 134.

With reference now to FIG. 10, a typical grid of LED heat lamps, whichis fashioned from the bottom array of LED lamps 148, is illustratedtherein. During processing, a wafer (not shown) is located on thesusceptor 134 and within the chamber 130. The wafer rests on thesusceptor 134 and is positioned generally above the bottom array of LEDlamps 148. The reactant gas flow direction 170 through the chamber 130is also shown. It should be noted that, in some chambers, the top arrayand the bottom array can be constructed differently.

With reference now to FIG. 11, the grid shown in FIG. 10 is illustratedwith the susceptor 134 shown by dashed lines. The bottom array of LEDlamps 148 includes light emitting diode (LED) lamps 180. The LED lamps180 are located below the susceptor and are spread across the grid. Inthis arrangement, the bottom array 148 also accommodates the spot lamps150, the rotating shaft 140 and the gas supply tube 152 (see FIG. 9).Thus, the central region of the bottom array of LED lamps 148 does notadmit to full LED lamps 180 across its entire surface. To the contrary,in such a configuration, the top array of LED lamps 146 (see FIG. 9)would not have such obstructions and full LED lamps across its entiresurface are easily accommodated and implemented.

With continued reference to FIG. 11, in one arrangement of the grid, thearrays of LED lamps are rectangular and approximately ninety LED lampsmake up the bottom array of LED lamps. The top array of LED lamps 146(see FIG. 9) may include a similar number of LED lamps. In anotherrectangular embodiment, each square inch of the grid comprisestwenty-five LED lamps. Continuing with this embodiment, if the grid areais sixteen inches by sixteen inches, then twenty-five LED lamps×256square inches˜6,400 LED lamps would be located in the bottom grid. In analternate arrangement of the grid, the LED lamps are circular in theirarrangement with the LEDs arranged in concentric circles. It should benoted that other numbers of LED lamps can be used in the selectedarrangement. Moreover, the number of LED lamps in the top grid can bedifferent than the number of LED lamps in the bottom grid.

A plurality of the LED lamps from the top or bottom grid can bephysically grouped so as to facilitate their removal and replacementwithin their respective grid. In one embodiment, the number of LED lampsin a group ranges from fifty to two hundred and fifty. These groups canbe configured as a module that plugs into an underlying base. The baseprovides electrical contacts.

The LED lamps 180, individually or in groups, advantageously reducetemperature gradients within the chamber such that nonuniformities intemperature across a wafer can be reduced or eliminated. To that end,nonuniformities in temperature within the chamber or nonuniformitiesacross the wafer processed within the chamber can be measured orestimated to determine relative cold spots or hot spots. Once anonuniformity has been found, one or more of the LED lamps within thearrays can be adjusted to provide differential power output across aregion of the array. The temperature gradient within the chamber and,therefore across the wafer, can be greatly reduced and the uniformity ofthe product can be improved. It should be noted that temperaturenonuniformities can be determined in any suitable manner, including butnot limited to, direct temperature measurements of the wafer, indirecttemperature measurements (i.e., measuring temperature within thechamber) or measuring the thickness of the processed materials.

In one embodiment, the LED lamps 180 operate in response topre-programming. In this embodiment, the LED lamps vary their heatoutput over time based on the pre-programming. In another embodiment, afailure of one or more LED lamps 180 is detected and compensated for byoperational LED lamps 180.

With reference to FIG. 12, a cross-sectional drawing of a portion of thearray 148 with one arrangement of a row of LED lamps is shown. The rowcomprises LED lamps 180(a)–180(f) covered by a perforated reflectorlayer 181. The perforated reflector layer 181 is coupled to supports184(a)–(f). The supports 184(a)–(f) and the LED lamps 180(a)–(f) areboth coupled to a printed circuit board 186.

In one embodiment, the LED lamps 180(a)–180(f) include gallium aluminumarsenide (GaAIA) infrared emitting diodes enclosed in a transparentplastic case. For example, types OP290, OP291, and OP292 of diodesmanufactured by Optek Technology, Inc. of Carrollton, Tex. can be used.Each LED lamp 180 is positioned to emit electromagnetic radiation in afocussed beam towards the susceptor 134 (see FIG. 11). Each LED lamp 180generally comprises two connectors, an anode and a cathode (not shown),disposed at the interface with the PCB 186. The two connectors extendinto the LED lamp 180 and are electrically connected to a diode locatedtherein. Thus, when a power is applied across the two connectors, thediode provides a source of radiant energy from its distal end in amanner generally known to those of ordinary skill in the art. LED Lamps180(a)–(f) can have varied dimensions depending upon the application andsize desired.

The perforated reflector layer 181 is formed of a reflective materialwith perforations or apertures 182(a)–(f) formed therein. The apertures182(a)–(f) substantially align with the LED lamps 180(a)–(f) to permitthe electromagnetic radiation emitted by the LED lamps 180(a)–(f) topass through the reflector layer 181. The shape of the apertures182(a)–(f) can be selected to compliment the irradiance pattern of theLED lamps. For example, a round shape can be selected for embodimentswhere each of the LED lamps 180(a)–(f) emits electromagnetic radiationalong a cylindrical path towards the susceptor. Other aperture shapescan also be used. The apertures 182(a)–(f) can be sized so as to reducethe reflected electromagnetic radiation that impinges upon the LED lamps180(a)–(f). In this way, the reflector layer 181 reflectselectromagnetic radiation that was reflected towards the LED lamps180(a)–(f). The reflector layer 181 can comprise, for example, ametallic surface such as gold.

The perforated reflector layer 181 attaches to the supports 184(a)–(f).The supports 184(a)–(f) provide a barrier between adjacent LED lamps180(a)–(f). The supports comprise a metallic material, for example,aluminum. Alternatively, steel can be used.

The printed circuit board (PCB) 186 is well known in the art andprovides an electrical and mechanical interface for the LED lamps180(a)–(f). The PCB 186 also provides the interface to electronic heatercontrol circuitry, described with reference to FIG. 13. The PCB 186further provides an attachment surface for the supports 184(a)–(f).Depending on the arrangement and grouping of the LED lamps, one or morePCBs may be used to attach one or LED lamps thereto.

FIG. 13 is a schematic view of the heating system of the presentinvention and also shows electrical connections between a suitablecontrol circuit. The heating system comprises an upper array of LEDlamps 146, a lower array of LED lamps 148, transmitters 250, a heatercontrol module 252, and a temperature control input 254.

The upper and lower arrays of LED lamps, individually or in groups,electrically connect with the heater control module 252 via one or moreprinted circuit boards (PCB) 186. In one embodiment, the heater controlmodule receives one or more signal from the transmitters 250. Thesesignals can represent the temperatures that are measured by thethermocouples 102. The heater control module 252 can farther receivesignals in the form of temperature settings from the temperature controlinput 254. These temperature settings can be indicative of a temperatureprofile programmed for the operation of the chamber. Alternatively, thedesired temperature profile is directly programmed into the heatercontrol module 252. In another embodiment, the heater control module 252receives a signal from the upper and lower arrays of LED lamps 146, 148indicating that one or more LED lamps are not operating properly. Thissignal can identify, for example, a failed LED lamp, a misaligned LEDlamp, and an LED lamp that is performing out of specification.

In response to one, or more than one, of these various input signals,the heater control module 252 sends control signals to each LED lamp 180or groups of LED lamps. The control signals allow the heater controlmodule 252 to dynamically control the output of the LED lamps. In thisway, the heater control module 252 can, for example, compensate for afailed LED, vary the output of the LED lamps over time based on aprogram, and adjust the output of the LED lamps based on feedback fromthe chamber.

Each LED lamp in the upper or lower arrays of LED lamps can be operatedat different power levels by control signals produced by the heatercontrol module 252. Besides individual control, each lamp can becontrolled in groups. The groups of LED lamps controlled by the heatercontrol module 252 can comprise only LED lamps from the top or bottomarrays of LED lamps. In one embodiment, the groups of LED lamps compriseLED lamps from both of the top and bottom arrays of LED lamps.

In the illustrated arrangement of FIG. 13, ninety individual LED lampsare provided in the top array and eighty-nine individual LED lamps areprovided in the bottom array. The LED lamps receive differing levels ofpower such that the temperature gradient across the wafer can besubstantially uniform across all portions of the wafer surface. Each LEDlamp can be associated with a temperature control module based onfeedback from temperature sensors (e.g., the thermocouples 102, 104, 106of FIG. 8).

The LED heat lamps 180(a)–(f) have their connector ends connected withthe PCB 186. The LED heat lamps 180(a)–(f) are thus controlledindividually or as a group by the output signals from the heater controlmodule 252. The LED heat lamps 180(a)–(f) are presented as an example toillustrate how one or more LED lamps can be controlled by the heatercontrol module 252. As described above, the other LED lamps 180 in theupper and lower arrays of LEDs can be similarly controlled, individuallyor in groups, by the heater control module 252.

The directed lamps 150 (see FIG. 9) have their respective terminalscoupled by conductors (not shown) which are in turn coupled to receivethe control signals from the heater control module 252. Thus, each ofthe directed lamps 150 operates in unison to provide a concentrated heatenergy receiving zone at the center area of the susceptor 134.

When an input signal is received from the temperature control input 254to indicate the start of a deposition cycle, the heater control module252 responds by applying full power to the directed lamps 150, to theselected LED lamps 180 of the upper array of LED lamps 146, and to theselected LED lamps 180 of the lower array of LED lamps 148. That sameinput signal contains information indicative of a desired operatingtemperature at which the deposition cycle is to be accomplished. Theapplication of full power to the directed lamps 150 and to the selectedLED lamps of the upper and lower arrays of LED lamps 146, 148 produces arapid rise in the temperature in the central area of the susceptor 134,and of course, in the central area of the wafer being processed. Amaster temperature sensor (not shown) located within the shaft 152senses the rapid rise in temperature and sends signals indicativethereof to the electronic heater control circuitry 152. The electronicheater control circuitry 152 compares the sensed temperature with thedesired operating temperature and adjusts the power supplied to thedirected lamps 150 and the selected LED lamps of the upper and lowerarrays of LED lamps to produce and maintain the desired operatingtemperature in the central area of the susceptor 134 and wafer.

While the temperature in the central areas of the susceptor 134 and thewafer are being brought up to the desired operating temperature, thetemperatures about the periphery of the susceptor 134 and in thetemperature compensation ring 72 are simultaneously being brought up totemperature by the selected LED lamps of the upper and lower arrays ofLED lamps. The increasing temperatures in the peripherally locatedheating zones or regions are sensed by the thermocouples 104 andadditional sensors if desired. The thermocouples produce signalsindicative of the sensed temperatures to the transmitters 250. Thetransmitters 250 provide these signals to the heater control module 252.The signals received by the heater control module 252 from thetransmitters 250 are compared with the signal received from the mastertemperature sensor to adjust the power to the selected LED lamps tobring the temperatures in the peripherally located heating zones intoalignment with the temperature in the central area of the susceptor 134and the wafer.

Due to variables such as heat losses at the peripheral edges of thewafer and the susceptor 134, the flow of reactant gas through thechamber 10, and the like, the LED heating lamps 180 may be ideally setto normally operate at temperatures which are offset, i.e. differentthan the desired operating temperature in the central area of the waferand the susceptor 134. And, the process of sensing temperatures andadjusting the power applied to the various groups, or banks of LEDheating elements as needed, is continued throughout the depositioncycle. The object of all this is, of course to provide a uniform, orflat temperature gradient in all of the relevant areas of the substrate,susceptor and temperature compensation ring throughout the depositioncycles. And in the interests of production time, to bring the system upto temperature as fast as possible at the beginning of a cycle and coolit down when a cycle is completed. The rapid increasing of temperaturesat the beginning of a cycle, as described above, is accomplished by thedirected lamps 150 and selected LED lamps of the upper and lower arraysof LED lamps 146, 148 in combination with the master-slave temperaturesensor arrangement which effectively produced the temperature followingmode of operation. Cooling the system down at the end of a cycle isaccomplished by reversing the above heating-up procedure. In otherwords, the power applied to the directed lamps 150 and the selected LEDheating lamps proximate the center of the upper and lower arrays of LEDlamps is reduced and the temperature in the peripherally located heatingregion will follow along with the reduction of heat at the center areasof the wafer and the susceptor 134.

The term “module,” as used herein, means, but is not limited to, asoftware or hardware component, such as a processor, FPGA, or ASIC,which performs certain tasks. A module may advantageously be configuredto reside on the addressable storage medium and configured to execute onone or more processors. Thus, a module may include, by way of example,components, such as software components, object-oriented softwarecomponents, class components and task components, processes, functions,attributes, procedures, subroutines, segments of program code, drivers,firmware, microcode, circuitry, data, databases, data structures,tables, arrays, and variables. The functionality provided for in thecomponents and modules may be combined into fewer components and modulesor further separated into additional components and modules.Additionally, the components and modules may advantageously beimplemented to execute on one or more computers.

Although the present invention has been described in terms of a certainpreferred embodiments, other embodiments apparent to those of ordinaryskill in the art also are within the scope of this invention. Thus,various changes and modifications may be made without departing from thespirit and scope of the invention. For instance, various components maybe repositioned as desired. Moreover, not all of the features, aspectsand advantages are necessarily required to practice the presentinvention.

1. A chemical vapor deposition apparatus comprising: a housing; asusceptor having a top surface and a bottom surface, and being disposedwithin the housing for supporting a wafer to be processed; atwo-dimensional array of light emitting diodes (LEDs) disposed along afirst axis and a second axis non-parallel to the first axis, the LEDsbeing configured to emit radiant energy through the housing and in adirection towards the susceptor; and a controller configured to vary theradiant energy emitted by a first LED arranged along the first axisrelative to a second LED arranged along the first axis, the controllerfurther configured to vary the radiant energy emitted by a first LEDarranged along the second axis relative to a second LED arranged alongthe second axis.
 2. The apparatus of claim 1, wherein the housingcomprises a top member, and wherein a substantial portion of the emittedradiant energy passes through the top member.
 3. The apparatus of claim2, wherein the top member is substantially transparent to radiantenergy.
 4. The apparatus of claim 1, wherein the emitted radiant energyis emitted in a direction towards the top surface.
 5. The apparatus ofclaim 1, wherein the housing comprises a bottom member, and wherein asubstantial portion of the emitted radiant energy passes through thebottom member.
 6. The apparatus of claim 5, wherein the bottom member issubstantially transparent to radiant energy.
 7. The apparatus of claim1, wherein the emitted radiant energy is emitted in a direction towardsthe bottom surface.
 8. The apparatus of claim 1, wherein the emittedradiant energy includes infrared radiation.
 9. The apparatus of claim 1,wherein at least a portion of the housing is made of quartz.
 10. Theapparatus of claim 1, wherein the controller is configured to respond toa failure by at least one of the LEDs.
 11. The apparatus of claim 1,wherein the controller is configured to respond to a signal indicativeof a temperature.
 12. The apparatus of claim 1, wherein the controlleris configured to respond to preprogramming.
 13. The apparatus of claim1, further comprising a temperature sensor configured to generate asignal indicative of a temperature in the housing.
 14. The apparatus ofclaim 1 further comprising a support plate that defines an opening thatis asymmetric relative to the susceptor.
 15. The apparatus of claim 14,further comprising a temperature compensation ring surrounding thesusceptor within the opening.
 16. The apparatus of claim 14, wherein theopening has a generally rectangular shape.
 17. The apparatus of claim 1,wherein a temperature of the housing is lower than a temperature of thesusceptor.
 18. A method of processing a semiconductor in a chamber byapplying heat from light emitting diode (LED) lamps, the LED lamps beingconfigured to emit directional radiant energy towards a substrate in thechamber, the method comprising: inserting a wafer in a chamber, thechamber being formed within a housing; applying radiant heat from atwo-dimensional array of light emitting diodes (LEDs) disposed along afirst axis and a second axis non-parallel to the first axis, the radiantheat passing through at least a portion of the housing and onto thewafer; adjusting the radiant energy emitted by a first LED arrangedalong the first axis relative to a second LED arranged along the firstaxis; and adjusting the radiant energy emitted by a first LED arrangedalong the second axis relative to a second LED arranged along the secondaxis.
 19. The method of claim 18, further comprising: identifyingnonuniformities in the temperature of the wafer; and adjusting an energylevel output of at least one of the LED lamps to compensate for thenonuniformity.
 20. The method of claim 19, wherein a temperature of theportion of the housing is lower than a temperature of the wafer.
 21. Asemiconductor processing apparatus comprising: a chamber defined by atleast one wall; a structure for supporting a substrate within thechamber; a two-dimensional array of light emitting diodes (LEDs)disposed along a first axis and a second axis non-parallel to the firstaxis, the array being disposed proximate to the chamber and configuredto emit radiant energy through the at least one wall and towards thestructure; and a controller configured to individually vary the radiantenergy emitted by LEDs arranged along the first axis, the controllerfurther configured to individually vary the radiant energy emitted byLEDs arranged along the second axis.
 22. The apparatus of claim 21,wherein the structure comprises a susceptor configured to contact thesubstrate.
 23. The apparatus of claim 21, wherein the two-dimensionalarray of light emitting diodes (LEDs) comprises a first LED heat lampand a second LED heat lamp, the first LED heat lamp being configured toemit directional radiant energy through the at least one wall andtowards a first location on the substrate and the second LED heat lampbeing configured to emit directional radiant energy through the at leastone wall and towards a second location on the substrate, the firstlocation being different than the second location.
 24. The apparatus ofclaim 23 further comprising a plurality of temperature sensing devicesconfigured to sense temperatures on the substrate proximate to the firstand second locations.
 25. The apparatus of claim 24, wherein thecontroller is configured to respond to the temperatures.
 26. Anapparatus for processing semiconductor wafers at elevated temperatures,the apparatus comprising: a high temperature processing chamber definedby at least one wall; a susceptor disposed within the chamber andcomprising a top surface, a bottom surface, a perimeter; a firsttwo-dimensional array of light emitting diode (LED) heat lamps beingdisposed along a first axis and a second axis non-parallel to the firstaxis, the array being disposed proximate to the susceptor; at least oneLED lamp of the first array of LED heat lamps configured to emitdirectional radiant energy through the at least one wall and in a firstpath towards the top surface; a controller configured to vary theradiant energy emitted by a first LED arranged along the first axisrelative to a second LED arranged along the first axis, the controllerfurther configured to vary the radiant energy emitted by a first LEDarranged along the second axis relative to a second LED arranged alongthe second axis; a second two-dimensional array of LED heat lamps beingdisposed proximate to the susceptor, the susceptor being disposedbetween at least a portion of the first array of LED heat lamps and thesecond array of LED heat lamps; and at least one LED lamp of the secondarray of LED heat lamps configured to emit directional radiant energy ina second path towards the bottom surface.
 27. The apparatus of claim 26,wherein at least a portion of the first path and at least a portion ofthe second path are located within a volume defined by the susceptorperimeter in a direction normal to the susceptor.
 28. A chemical vapordeposition apparatus, comprising: a process chamber having an area forhorizontal positioning of a substrate within a substrate treatment zoneand having chamber walls for conducting a flow of gas across a surfaceof the substrate; a first two-dimensional array of heat lamps beingdisposed generally above the substrate treatment zone, each LED of thefirst two-dimensional array of heat lamps having a length and a width sothat the first two-dimensional array of heat lamps spans the substratetreatment zone in a first row and spans the substrate treatment zone ina first column generally perpendicular to the first row; and acontroller configured to vary the radiant energy emitted by a first LEDarranged along the first axis relative to a second LED arranged alongthe first axis, the controller further configured to vary the radiantenergy emitted by a first LED arranged along the second axis relative toa second LED arranged along the second axis.
 29. The apparatus of claim28 further comprising a second two-dimensional array of heat lamps beingdisposed generally below the substrate treatment zone, each LED of thesecond two-dimensional array of heat lamps having a length and a widthso that the second two-dimensional array of heat lamps spans thesubstrate treatment zone in a second row and spans the substratetreatment zone in a second column, at least one LED from the second rowor second column having means for adjusting energy lamp output relativeto another of the LEDs from the same second row or column.